Patent GB-396720-A (GB)
Title: Improvements in automatic switches for use in telephone or like systems
IPC: H04Q3/00
Filed: 1932-02-08
Abstract: 396,720. Automatic exchange systems. AUTOMATIC ELECTRIC CO., Ltd., Strowger Works, Liverpool, BEALE, C. E., 59, Towers Road, and TAYLOR, R., 30, Oulton Road, both in Wavertree, Liverpool. Feb. 8, 1932, No. 3732. [Class 40 (iv).] Bi-directional selectors, of the type that, on release, move to the twelfth rotary position restore vertically and then rotate to the normal position, are provided with the following features : (i) the secondary magnet circuit is completed, during the releasing motion of the switch, over a back contact of the switching relay and off-normal contacts ; (ii) the change-over relay interacts with the secondary magnet ; (iii) the secondary magnet interacts with a relay in common equipment during the setting motion and with an individual relay during release ; (iv) the primary and secondary magnets interact during the release movement, the primary magnet being unable to affect the mechanical operation of the switch at this time. The switch is guarded during release by the reoperation of the impulse responding relay. Specifications 376,265 and 391,123 are referred to. Fig. 2 shows the invention as applied to a group selector with two sets of wipers. When the switch is seized 1A energizes followed by 1B and the impulse train is repeated to 1VM. When the train terminates, 1C which was energized in parallel to 1VM, releases and 1RM rotates the wipers on to the first contacts. If P1 encounters earth 1C re-energizes opening the circuit of 1RM, which releases, and completes circuits from P2 to its own lower winding and to HB. If P2 also encounters earth the lower winding of 1C is energized and, as the windings are in opposition, the relay falls away allowing 1RM to re-energize and step the wipers. This cycle is repeated until a free circuit is reached. If P1 encounters the free outlet 1C is not re-energized and HA, being no longer shorted; pulls up, locks, opens the circuits of 1RM and switches through. If P2 encounters the free outlet HB pulls up and switches through but 1C does not fall away until HB has opened the circuit of 1RM. In either case 1A falls away but 1B is sufficiently slow to release to hold the connection until earth is returned from the succeeding selector. If all outlets are busy the wipers - 1 and + 1 encounter contacts 21, 22 and cam springs 1S1, 1S2, 1S3 are operated. Relay HA pulls up, busy tone is returned over 1A and overflow meter 1OVF is operated. When the calling subscriber clears the operated switching relay falls away, 1A pulls up to retain guarding earth, and 1RM energizes and interacts with 1C to step the wipers to the twelfth position where they restore verticallv and are rotated into the normal position. The application of the invention to a finder switch which is operated from common equipment of the type disclosed in Specification 376,265 is shown in Fig. 4. When a call is initiated marking is placed on both vertical and rotary banks and 3HB is energized over wiper 7 of 3PDS. The vertical magnet is energized over wiper 8 and 3VM interacts with a relay (not shown) in the common equipment and connected to wiper 3 to raise the finder. When 3VW encounter's the marked level, the marking is connected over wiper 5 and as a result 3HA is energized over wiper 6, changing over to the rotary magnet RM. The relay in the common equipment is now connected over 1 of 3PDS and now interacts with 3RM to rotate the wipers until the marked' contact is reached when the finder stops and the unwanted switching relay is released. When the calling subscriber replaces his receiver the operated switching relay releases and 3G and 3RM interact directly to step the switch into its twelfth rotary position when the switch restores as already described. A finder switch in which the relay 3G is not provided and in which 3RM and 3VM interact to step the switch during the releasing movement is also described.